Hydraulic circuit



Aug. 13, 1940. w. ERNST ET AL 2,211,370

HYDRAULIC CIRCUIT Filed July 1, 1957 a w PM. W ex e Tscv n3 n u n ENGT W mama 5n I N 45, n5 m wsw y 3 ow mm v 2N NM mm MNNQ mv Patented Aug. 13, 1940 d UNITED STATES HYDRAULIC CIRCUIT Application July 1, 1937, Serial No. 151,470 7 Claims. (CI. 6052) This invention relates to hydraulic machine circuits, and in particular, to circuits for operating hydraulic machines having multiple hydraulic motors-and pistons therein.

One object of this invention is to provide a hydraulic machine circuit for operating a hydraulic machine having a plurality of motors with'a plurality of pumps. for operating the motors, together with devices for unloading both of the pumps whenever they are not required to do useful work.

Another object is tb'provide a hydraulic machine circuit, wherein-two hydraulic motors are operated from cooperating constant delivery and variable delivery pumps in such a manner that one of the pumps is caused to idle at substantially zero pressure when it is not required to supply pressure fluid.

Another object is to provide a hydraulic machine circuit, wherein two hydraulic motors are operated from two hydraulic pumps, one of the motors having a check valve device in the piston thereof, arranged to unload both pumps when the piston is in its retracted position, as when the n achine'is at rest.

Another object is to provide a hydraulic machine circuit, wherein two hydraulic motors are operated by two hydraulic pumps in such a manner that one of the pumps is fully unloaded when the machine is at rest, with its pistons in av retracted position, and wherein the two pistons may be operated simultaneously or independently to a limited extent on both their retraction and advancement strokes.

Another object is to provide a hydraulic machine circuit, wherein two pumps are caused to supply pressure fluid to two hydraulic motors in such a manner that both of the pumps are fully unloaded when the machine is at rest, with its pistons in a retracted position, and wherein'the two pistons may be operated simultaneously or independently to a limited extent ever they are not required to do useful work. a

In general, the hydraulic machine circuit shown in Figure 1 has the purpose of enabling the operation of two independent hydraulic motors from a pair of pumps. One of the pumps is a low pressure constant delivery type, whereas the other is a high pressure variable delivery type. The circuit is arranged with devicesffor causing the high pressure pump to unload the low pressure'pump when the latter has performed its work, the high pressure pump being employed to maintain pressure upon one of the motors while the other motor is being operated. When the pistons of both motors reach their retracted positions, devices are provided for unloading the discharges of both pumps at substantially zero pressure.

Hydraulic circuit for operating motors Referring to the drawing in detail, Figure 1 shows the hydraulic machine circuit of this invention as consisting of a tank ill from which lines Ill and I2 leaditd the variable delivery high pressure and constant delivery low pressure pumps I3 and M, respectively. From the low pressure constant delivery pump I4 the line I5 leads to thepressure relief valve, generally designated Hi, from which the line ll leads to the ball check valve I8, continuing in the line I!) joining the line 20, which terminates at one end in the port 2| of the first operating valve, generally designated 22. The variable delivery pump l3 discharges directly into the line- 20, and hence, both pumps l4 and I3 cooperate to supply pressure fluid to the port H of the first pump. This variable delivery pump I3 is provided with a control mechanism, of a type known to those skilled in the art, and forming no part of the present invention. This control permits the pump to be shifted to a neutral or zero stroke position, and' to maintain pressure in the circuit when this pressure is built up to a predetermined value. A pump control of this type,.is"

disclosed in the Ernst Patent No. 2,039,893, is-

sued May 5, 1936. The low pressure constant de-' livery pump 14 may likewise be of" any suitable conventional type, such as the gear or vane type,

and its details form no part of the present invention. r

The pressure relief valve I6 is of a conventional type, and a complete disclosure thereof will be way 26 interconnecting the main valve chamber 2! and the plunger-lifting chamber 28, the fiow being adjustable by means of a needle valve 29. The plunger 23 within theplunger-lifting chamber 29 is provided with an annular shoulder 30, which serves as a piston area, to lift the plunger 23 when the pressure exceeds a predetermined amount, as determined by the force of the spring 26. When this amount is exceeded and the pressure lifts the plunger 23, the fluid from the constant delivery pump i4 passes from the plungerlifting chamber 2! downwardly, through the pipe 3|, into the tank i0.

The first operating valve 22 consists of a longltudinally bored casing 32 having a valve rod .33 with twin spaced heads 34 and 35 thereon.

These heads open into spaced chambers 36, 31, 33 and 39 and 40. The chambers 36 and 40 open into the ports 4| and 42, connected by the line 43 to the tank Ill. The chamber 38 opens into the port 2| and line 20, previously described. The chambers 31 and 39 open into the ports 44 and 45, to which are attached the lines 46 and 41, respectively. The line 41 leads to the port 48 in the main hydraulic cylinder 49. The latter has a piston50 with a head 5| reciprocating therein. The line 46 is connected to the port 52 at the right-hand end of the cylinder 49. A port 53 is provided at the left-hand end of the auxiliary cylinder 54. The latter is provided with a piston 55 having a head 56.

The opposite end of the cylinder 54 is provided with a port 51 connected by the line 58 to the port 59 of the second operating valve, generally designated 60. The latter is of a similar construction to the first operating valve 22, and its corresponding parts bear similar numerals. The outlet ports, however, are differently designated for purposes ofclarity. Fromthe end ports 6| and 62 the line 63 runs downwardly to the tank l0. From the middle port 64 the line 65 runs to a junction with the line H, between the check valve I8 and the pressure relief valve l6. From the remaining port 66 the line 61 runs to the port 53 of the cylinder 54. The line 58 also runs through the check valve 66 to the pilotoperated unloading valve, generally designated 69.

- The latter is provided with a valve chamber 10 and a plunger-lifting chamber 1|, having pressure fluid supplied thereto by the pilot line I2 leading from the pressure line 20 of the high pressure variable delivery pump l3.

The unloading valve 69 contains a plunger 13 having an annular shoulder 14 forming a piston area within the plunger-lifting chamber 1|, and\ ur ed downwardly by the coil spring 15 within the casing 16. The pressures at which the pressure relief valve l6 and unloading valve 69 open may be adjusted by turning the screw caps 19 and 80, with which these valves are equipped. The unloading valve 69 is also provided with a reduced diameter portion below the valve chamber 10, and forming -an additional chamber '18 into which the lower end 1'! of the valve plunger 13 operates. This chamber is connected by the line 58, containing the check valve 68, to the port 51 of the hydraulic cylinder 54. The latter also is provided with an additional port 8|, located atapproximately the point where it will be un covered when the piston head 56 reaches its retracted position. From the port 8| the line 82 runs to the port 83 opening into the valve chamber i0,

The piston head 5| and piston 50 of the main hydraulic cylinder 49 are provided with a special check valve device, which is forcibly opened when the piston reaches its retracted position. For this purpose the piston 50 is provided with a port ||6 opening into a right-angled passageway H5, terminating in an enlarged chamber 099 containing a ball 3, and having a passageway opening from the opposite end of the chamber H19 into the space at the left-hand side of the piston head 5|. The end of the main cylinder 49 is provided with a threaded bore H1 carrying a threaded valve-operating member H8 having a valve-operating tip H9, The latter is adapted to extend through the passageway HI and unseat the ball 3 when the piston head 5| reaches its retracted position at the extreme lefthand end of the main cylinder 49.

In practice, the passageway I of this check valve mechanism is provided with a valve seat 2. Similarly, the end of the passageway H5 is provided with a valve seat 4. By reason of the foregoing construction the piston halts instantly when the ball 3 is unseated by the action of the projecting member I I9, after which pressure is released and fluid passes freely through the piston head 5|. The plunger 59 containing the check valve 3 is described and claimed in itself in the copending application of Ernst and Geiger, Ser. No. 148,339, filed June 15, 1937.

Operation To perform a working stroke, the operator starts the pumps l3 and I4 and shifts the first operating valve 22 into the opposite position from that shown in Figure 1 so that the circuit is opened between the lines 20 and 41. When this is done the circuit will also be opened between the pull-back line 46 and the discharge line 43 running back to the tank l0. Under these conditions the pressure fluid in the line 20 coming from the pumps l3 and [4 will pass through the line 41 into the left-hand end of the cylinder 49. This fluid forces the ball 3 to the right against the seat Ill, closing the passageway 5 through the piston head 5|. The latter then moves forward to the right, and does its work, such as clamping a pair of dies. The fluid displaced from the forwardiend of the cylinder 49 passes through the line 46, the first operating valve 22 and the line 43, back to the tank I.

, 21 of the unloading valve l6, the conduits I1 and 65, the four-way valve 60, the conduit 61, the port 53, the cylinder 54, the port 8|, the conduit 52, the unloading valve chamber 10, past the now lifted plunger 13, the conduit 58, through the check valve 68, the four-way valve 60 and the conduit 63 to the tank I0. Meanwhile, the check .valve I8 has been closed by the backing up of pressure in the conduit I9. The pressure continues to build up in the left-hand end of the cylinder 49 andcauses a consequent building up of pressure in the lines 41 and 20. When this pressure reaches a predetermined value, accord-I ing to the setting of the pump control of the variable delivery pump N, the control mechanism moves the flow-control member of the pump to its no delivery or neutral position.

The operator next shiftsthe second operating Shifting of valve 50 shuts off the above-described to the end of its stroke.

by-pass of the low pressure pump |4 therethrough by way of the unloading valve 69. The pressure admitted to the cylinder 54 through the line 58 and port 51 moves the piston head 56 forward. The fluid displaced from the forward end thereof passes through the port 53, the line 51, the valve 60 and the line 53, into the tank l0. Since the variable delivery pumpl3 at this time is developing the maximum pressure for which its control is set, the unloading valve 59 is held open by pressure from the line 12 acting against the piston area it within the plunger-raising chamber H. Fluid cannot back up through the line 53 to the unloading valve 69, however, because such pressure instantly closes the check valve 68 so that no fluid escapes by this route. Urged by -the fluid in the right-hand end of the cylinder 54, the piston head 55 moves forward The consequent rise in pressure in the discharge circuit of the low pressure pump it then backs up in the chamber 21 of the pressure relief valve i8 and passes through the plunger passageway 26, into the plunger-lifting chamber 28. There it acts against the annular piston area 30 and raises the valve plunger 23 sufilciently to release theexcess discharge of the low pressure pump I4 through the conduit 3| to the tank III. In this way the work can be held with the plunger 50 while other work is being done with the plunger 55.

To retract the piston head '56 the operator shifts the second operating valve 50 to the position shown in Figure 1, whereupon-the circuit is opened between the lines 58, and 63, permitting fluid to escape from the right-hand end of the cylinder, back to the tank Ill. The same shifting admitted moves the piston head 56 to the right.

until ituncovers the port 8|. As the unloading valve 69 is still kept open by the pressure from the variable delivery pump l3 in the line 12, the

fluid subsequently delivered to the cylinder 54 from the lines 65 and 6'! now escapes through the port 3|, line 82, chamber E of the unloading valve 69, line 58, check valve 68, ports 59 and 6| of the second'operating valve. 60, and line 63,

back to the tank Ml. In this manner the fluid flowing to the forward end of the cylinder 54 is by-passed back to the tank ill.

To reverse the motion and retract the piston head 55, the operator now shifts the first op-- erating valve 22 to the position shown in Figure 1, thereby opening the circuit between the lines 2@ and Q6, and also between the lines 6'! and 43. Pressure fluid now flows from the lines l9 and 2d through the first operating valve 22 fluid then causes the piston head to move to the left. Because a maximum pressure is not required to retract the pistonhead 5|, a pressure.

drop occurs in the line 72, relieving the pressure inthe chamber H of the unloading valve 69, causing the latter to close. This cuts off the bypass of pressure fluid from the cylinder 54, through the port 8|, and line 82, thereby-causing both of the pumps I3 and H to subsequently discharge their fluid into the cylinder 49.

The piston head 5| moves rearwardly until the projection M9 upon the threaded member H8 strikes the ball H3 and pushes it from its seat.|l2. This opens the passageway Hi and permits the fluid to escape subsequently through the right-angled passageway M5, the chamber Hi9, the passageway iii, the port 38, the line 61, the first operating valve 22 and the line 43, back to the tank it). The piston head 5| immediately halts because of this by-passing of the fluid, and the pumps 63 and it subsequently discharge at substantially zero pressure into the tank it.

It will be understood that we desire to comprehend within our invention such modifications as come within the scope of the claims and the invention.

Having thus fully described our invention, what we claim as new and desire to secure by Letters Patent, is: i

1. In a hydraulic machine circuit, a pair of cylinders, pistons in said cylinders, a high pr essure pump and alow pressure pump connected to one of said cylinders, one of said pumps being connected to the other cylinder, valve means in said circuit responsive to the development of a predetermined pressure in said circuit for by-passing the flow of pressure fluid from said low pressure pump, and means responsive to the arrival of one of said pistons at a predetermined position for by-passing the flow of pressure fluid from both of said pumps.

2. In a hydraulic machine circuit, a pair of cylinders, pistons in said cylinders, a high pressure pump and a low pressure pump connected to one of said cylinders, one of said pumps being connected to the other cylinder, valve means in said circuit responsive to the development of a predetermined pressure in said circuit for bypassing the flow of pressure fluid from said low' pressure pump, and means responsive to the arrival of one of said pistons at a predetermined position on the retraction stroke thereof for bypassing the flow of pressure fluid from both of said pumps.

3. In a hydraulic machine circuit, a pair of cylinders, pistons in said cylinders, a high pressure pump and a low pressure pump connected to one of said cylinders, one of said pumps being connected to the other cylinder, a pair of pressure-responsive valves in said circuit adapted to cause "Dy-passing of the low pressure pump, one of said valves beingopenable in response to the development ofa predetermined pressure by said high pressure pump and the other openable in response to the development of a predetermined pressure by said low pressure pump only/, and means responsive to the arrival of one of said pistons at a predetermined position for by-passing the flow of pressure fluid from both of said 4. In a hydraulic machine circuit, a pair of cylinders, pistons in said cylinders, a high pressure pump and a low pressure pump connected to one of said cylinders, one of said pumps being connected to the othercylinder, a pair of pressure-responsive valves in said circuit adapted to cause by-passing of the low pressure pump, one of said valves being openable in response to the development of a predetermined pressure by said high pressure pump'and the other openable in response to the development of a predetermined pressure by said low pressure pump only, and means responsive to the arrival of one of said pistons at a predetermined position on themetraction stroke thereof for by-passlng the flow of pressure fluid from both of said pumps.

5. In a hydraulic machine circuit, a pair of cylinders, pistons in said cylinders, a high pressure pump and a low pressure pump connected to one of said cylinders, one of said pumps being connected to theother cylinder, a pair of pressure-responsive valves in said circuit adapted to cause by-passing of the low pressure pump, one of said valves being openable in response to the development of a predetermined pressure by said high pressure pump and the other openable in response to the development of a predetermined pressure by said low pressure pump only, and means associated with the head of one of said pistons and responsive to its arrival at a predetermined position for by-passing the flow of pressure fluid from both of said pumps.

6. In a hydraulic machine circuit, a pair of cylinders, pistons in said cylinders, a high pressure pump and a low pressure pump connected to one of said cylinders, one of said pumps being connected to the other cylinder, a pair of pressure-responsive valves in said circuit adapted to cause by-passing of the low pressure pump, one

of said valves being openable in response to the (3 development of a predetermined pressure by said high pressure pump and the other openabie in response to the development of a predetermined pressure by said low pressure pump only, and

means responsive to the arrival of one of said-'10 pistons at a predetermined position for bypassing the flow of pressure fluid from both of said pumps, one of said pistons being connected in said circuit for advancement by pressure fluid from said low pressure pump only. 16

WALTER ERNST. GEORGE M. GEIGER.

WARREN R. TUCKER. 

